WATER SUPPLY OP PASTERN AND SOUTHERN FLORIDA. 139 
AMOUNT OF HYDROGEN SULPHIDE INFLUENCED BY 
PRESSURE. 
The quantity of H2S gas, which the water is able to hold in 
solution under these conditions, is determined by the pressure. 
The law of the solubility of gases in liquids is as follows: The 
quantity of the gas which the liquid is able to dissolve is directly 
proportional to the pressure on the gas. In the open, porous 
limestone with no confining stratum above, the water at the top 
of the underground water level is merely under atmospheric 
pressure. After passing the underground water level, however, the 
pressure increases rapidly. The increase of pressure is not simply 
that due to the atmosphere, but that due to the weight of the 
overlying column of water plus the atmosphere. According to 
Van Hise:* “The pressure, which really is determinative as to 
the amount of gas which may be held in solution, is that of a 
column of water extending to the free surface, plus the atmos¬ 
pheric pressure.” From this law it follows that water, at a great 
depth and under great pressure, is capable of holding a large 
quantity of hydrogen sulphide in solution. When brought to the 
surface the pressure is relieved and the gas rapidly escapes. The 
artesian waters, in the flowing areas of the State, are under con¬ 
siderable pressure, thus enabling them to hold a large quantity of 
hydrogen sulphide as well as a high proportion of mineral solids 
in solution. 
In order that the deep waters may hold large quantities of 
H2S in solution, it is necessary that the gas be available. This 
implies that the gas in the artesian and other deep waters 
originates at some considerable depth rather than at or near the 
surface. 
ARTESIAN WATER. 
The term “artesian’'’ has been variously used by different 
writers. Flowing wells first became well known in the province 
of Artios, France, and hence were called “artesian wells,” and 
*L. c., page 70. 
